Reverse water gas shift catalytic reactor systems

ABSTRACT

The present invention describes a processes, systems, and catalysts for the utilization of carbon dioxide into high quality synthesis gas that can then be used to produce fuels (e.g., diesel fuel) and chemicals. In one aspect, the present invention provides a process for the conversion of a feed gas comprising carbon dioxide and hydrogen to a product gas comprising carbon monoxide and water.

FIELD OF THE INVENTION

The present invention describes an improved catalytic reactor andassociated processes, for the utilization of carbon dioxide into highquality synthesis gas that can then be used to produce fuels (e.g.,diesel fuel, jet fuel, gasoline, kerosene, others), chemicals, and otherproducts.

BACKGROUND OF THE INVENTION

Carbon dioxide is produced by many industrial and biological processes.Carbon dioxide is usually discharged into the atmosphere. However, sincecarbon dioxide has been identified as a significant greenhouse gas,these carbon dioxide emissions need to be reduced from these processes.Although carbon dioxide can be used to enhance oil and gas recovery fromwells in limited cases, the majority is emitted into the atmosphere. Thepreferred method to deal with carbon dioxide is to efficiently captureand utilize the carbon dioxide and convert it into useful products suchas fuels and chemicals that can displace fuels and chemicals producedfrom fossil sources such as petroleum and natural gas and thereforelower the total net emissions of carbon dioxide into the atmosphere.

One reaction that has been considered for utilization of carbon dioxideis the Reverse Water Gas Shift (RWGS) reaction which is often referredto as carbon dioxide hydrogenation.

CO₂+H₂

CO+H₂O

This reaction converts carbon dioxide and hydrogen to carbon monoxideand water. This reaction is endothermic at room temperature and requiresheat to proceed. Elevated temperature and an efficient catalyst arerequired for significant carbon dioxide conversion to carbon monoxidewith minimal or no coking (carbon formation).

Hydrogen (H₂) can be produced from many sources including natural gas ormore preferably from water via electrolysis or other means.

${H_{2}O} = {H_{2} + {\frac{1}{2}O_{2}}}$

With the CO (Carbon Monoxide) from the RWGS reaction and H₂ from theelectrolysis of water, one has the potential for useful products.Mixtures of H₂ and CO are called synthesis gas or syngas. Syngas may beused as a feedstock for producing a wide range of chemical products,including liquid and gaseous hydrocarbon fuels, alcohols, acetic acid,dimethyl ether and many other chemical products.

Several catalysts have been disclosed for the RWGS reaction. The primarycatalysts studied previously were Cu or Pt or Rh dispersed on metaloxide supports. (Daza & Kuhn, RSC Adv. 2016, 6, 49675-49691).

Despite certain reports, there is still a need for novel processes,systems and catalysts related to the RWGS chemical reaction.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 shows an integrated high efficiency process for the hydrogenationof carbon dioxide using Reverse Water Gas Shift and a unique processscheme for efficient conversion.

FIG. 2 shows a general arrangement of the unique Reverse Water Gas Shiftreactor and associated equipment. Specifically, FIG. 2 shows a crossexchanger to preheat the feed H₂ and CO₂ with the hot syngas productsleaving the RWGS, followed by an electric heater to bring the H₂ and CO₂to reaction temperature, and finally the RWGS reactor vessel wherein isa catalyst which converts the H₂ and CO₂ to CO and H₂O.

SUMMARY OF THE INVENTION

The invention relates to a process for the conversion of a feed gascomprising carbon dioxide and hydrogen to a product gas comprisingcarbon monoxide and water. The feed gas is heated to an inlettemperature greater than 1,400° F., preferably greater than 1,500° F. ormore preferably greater than 1,600° F., at least partially in apreheater outside the main reactor vessel to produce a heated feed gas.The preheater uses electricity to generate heat and transfer the heatand produce the heated feed gas. The heated feed gas is sent to a mainreactor vessel. The main reactor vessel is an adiabatic or nearlyadiabatic vessel where heat loss is minimized. The main reactor vesselcontains a catalyst that converts the heated feed gas to product gas.The product gas leaves the main reactor vessel at an exit temperaturewhere the exit temperature is lower than the inlet temperature.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 shows a RWGS reactor flowsheet. Hydrogen is one of the feed gasesand can be produced by electrolysis of water.

$\left. {H_{2}O}\rightarrow{H_{2} + {\frac{1}{2}O_{2}}} \right.$

Hydrogen can also be produced by the steam reforming of hydrocarbonssuch as methane or natural gas.

CH₄+H₂O→3H₂+CO

Carbon dioxide can come from numerous industrial and natural sources.CO₂ is often found in natural gas deposits. CO₂ is emitted from manybiological processes such as anaerobic digestion. Many other processes(e.g., power plants, cement plants, ethanol production, petroleumrefining, chemical plants, etc.) produce carbon dioxide which is usuallydischarged into the atmosphere. CO₂ can also be found in the atmosphere.CO₂ can be captured from these biological, industrial, and atmosphericprocesses via many known technologies and can be used as feedstock forthe invention. H₂ stream 1 and CO₂ stream 2 are mixed to form stream 3in FIG. 1 . The ratio of H₂/CO₂ is between 2.5-4.5 v/v, and preferablybetween 3.0-4.0 v/v. The mixed feedstock can be heated by indirect heatexchange to a temperature of greater than 1,400° F. It is important thatthis initial temperature rise is done without the use of directcombustion of a carbon containing gas to provide the heat as that wouldmean that carbon dioxide was being produced and could possibly negatethe impact of converting carbon dioxide to useful fuels and chemicals.

The feed gas comprising a mixture of hydrogen and carbon dioxide isheated to an inlet temperature greater than 1,400° F., preferablygreater than 1,500° F., or more preferably greater than 1,600° F., atleast partially in a preheater unit 4 outside the main reactor vessel toproduce a heated feed gas. The pre-heater is electrically heated andraises the temperature of the feed gas through indirect heat exchange togreater than 1,400° F., preferably greater than 1,500° F., and morepreferably greater than 1,600° F. There are numerous ways that theelectrical heating of the feed gas can be done. One way is using anelectrically heated radiant furnace. In this embodiment, at least aportion of the feed gas passes through a heating coil in a furnace. Inthe furnace, the heating coil is surrounded by radiant electric heatingelements. In another embodiment of the invention, the gas is passeddirectly over heating elements whereby the gas is heated by convectiveheat transfer. The electric heating elements can be made from numerousmaterials. The most common heating elements are nickel chromium alloys.These elements may be in rolled strips or wires or cast as zig zagpatterns. The elements are fixed into an insulated vessel where ceramicfiber is generally used for insulation. The radiant elements may bedivided into zones to give a controlled pattern of heating. Multiplecoils and multiple zones may be needed to provide the energy to producea heated feed gas. Radiant furnaces require proper design of the heatingelements and fluid coils to ensure good view factors and good heattransfer. The electricity usage by the radiant furnace should be as lowas possible. The electricity usage by the radiant furnace is less than0.5 MWh (megawatt-hour) electricity/metric ton (MT) of CO₂ in the feedgas; more preferably less than 0.40 MWh/MT CO₂; and even more preferablyless than 0.20 MWh/MT CO₂.

The heated feed gas stream 5 then is fed into the main reactor vesselunit 6. There are two possible embodiments of the main reactor vessel.In the first embodiment, the main reactor vessel is adiabatic or nearlyadiabatic and is designed to minimize heat loss, but no added heat isadded to the main reactor vessel and the temperature in the main reactorvessel will decline from the inlet to the outlet of the reactor. In thesecond embodiment, the main reactor vessel is similarly designed butadditional heat is added to the vessel to maintain an isothermal ornearly isothermal temperature profile in the vessel. The main reactorvessel is tubular reactor with a length longer than diameter. Theentrance to the main reactor vessel is smaller than the overall diameterof the vessel. The main reactor vessel is a steel vessel. The steelvessel is insulated internally to limit heat loss. Various insulationsincluding poured or castable refractory lining or insulating bricks maybe used to limit the heat losses to the environment. (SeeHarbison-Walker Handbook of Refractory Practices, 2005,https://mha-net.org/docs/Harbison%20Walker%202005%20-Handbook.pdf).

A bed of catalyst is inside the main reactor vessel. The catalyst can bein the form of granules, pellets, spheres, trilobes, quadra-lobes,monoliths, or any other engineered shape to minimize pressure dropacross the reactor. Ideally the shape and particle size of the catalystparticles is managed such that pressure drop across the reactor is lessthan 50 pounds per square inch (psi) [345 kPa] and more preferably lessthan 20 psi [139 kPa]. The size of the catalyst form can have acharacteristic dimension of between 1 mm to 10 mm. The catalyst particleis a porous material with an internal surface area greater than 20 m²/g,more preferably greater than 30 m²/g. Several catalyst materials arepossible that can catalyze the RWGS reaction. The primary catalystsstudied previously were Cu or Pt or Rh dispersed on metal oxidesupports. (Daza & Kuhn, RSC Adv. 2016, 6, 49675-49691). We have foundthat the preferred catalyst is a supported catalyst, where the catalystis a catalyst that has high thermal stability up to 1,100° C., that doesnot form carbon (coking) and that has good resistance to contaminantspresent in captured CO₂ streams. The catalyst exhibits high activity atlow metal concentrations, such as 0.5-20 wgt %. The shape and particlesize of the catalyst are managed such that pressure drop across thereactor is less than 50 pounds per square inch or less than 20 poundsper square inch.

The catalyst used in the process is a high-performance catalyst that ishighly versatile, and which efficiently catalyzes the RWGS reaction.

The conversion of carbon dioxide to carbon monoxide in the main reactorvessel is generally between 60 and 90 mole % and more preferably between70 to 90 mole %. If the embodiment of an adiabatic reactor is used, thetemperature in the main reactor vessel will decline from the inlet tothe outlet. The main reactor vessel outlet temperature is 100-200° F.less than the main reactor vessel inlet temperature and more preferablybetween 105-160° F. lower than the main reactor inlet temperature. TheGas Hourly Space Velocity (GHSV), which is the mass flow rate ofreactants (H₂+CO₂) per hour divided by the mass of the catalyst in themain reactor bed, is between 1,000 and 60,000 hr⁻¹ and more preferably10,000 to 30,000 hr⁻¹.

The gas leaving the main reactor vessel is the product gas. The productgas comprises CO, H₂, unreacted CO₂, and H₂O. Additionally, the productgas may also comprise methane (CH₄) that was produced in the mainreactor vessel by a side reaction. In one embodiment, methane productionis preferably less than 10%, in another less than 5%, and in anotherless than 1%.

The product gas stream 7 can be used in a variety of ways at this pointin the process. The product gas can be cooled and compressed and used indownstream process to produce fuels and chemicals. The product gas canalso be cooled, compressed in unit 8, and sent back to the preheater andfed back to the main reactor vessel. The product gas can also bereheated in second electric preheater (unit 9) and sent to a secondreactor vessel (unit 10) where additional conversion of CO₂ to CO canoccur. Optional compression (unit 11) can be done before the CO and H(or Syngas) is sent to the liquid fuel synthesis step (stream 12).

FIG. 4 shows a general arrangement detail including the electric gaspre-heater, the RWGS reactor and the cross exchanger. The feed gascomprising a mixture of H₂ CO₂ enters the shell side of theshell-and-tube cross exchanger where it is heated by the tubescontaining the hot product gas leaving the RWGS reactor. The feed gas isthen further heated in the electric gas preheater unit whereelectrically resistive heating elements provide additional thermalenergy to raise the temperature of the feed gas to greater than 1,400°F., preferably greater than 1,500° F., and more preferably greater than1,600° F. The heated feed gas then goes into the RWGS reactor where theCO₂ and H₂ react over a packed bed of catalyst to form carbon monoxideand water. This reaction in endothermic, causing the temperature to dropwithin the RWGS reactor or requiring additional electrically resistiveheating elements to provide further thermal energy within the RWGSreactor to maintain temperature. The hot product gas from the exit ofthe RWGS reactor then enters the tube side of the cross exchanger whereit is cooled by the incoming feed gas.

Certain Reverse Water Gas Shift Method Embodiments

The following are certain embodiments of processes for the conversion ofcarbon dioxide to product gas using Reverse Water Gas Shift CatalyticReactor Systems:

-   -   1. Hydrogen and carbon dioxide are mixed and fed into the RWGS        catalytic reactor, where the RWGS reactor vessel is adiabatic or        nearly adiabatic. The main reactor vessel is an insulated steel        vessel, and it contains a catalyst bed including a supported        catalyst where the catalyst consists of one or more Group 1 and        Group 2 metals supported on a metal-alumina spinel. The RWGS        product gas exits the RWGS reactor vessel.    -   2. Hydrogen and carbon dioxide are mixed and fed into the RWGS        catalytic reactor, where the RWGS reactor vessel where heat is        added to the vessel to maintain an isothermal or nearly        isothermal temperature profile in the vessel; heating is        performed without the use of direct combustion of a carbon        containing gas. The main reactor vessel is an insulated steel        vessel, and it contains a catalyst bed including a supported        catalyst where the catalyst consists of one or more Group 1 and        Group 2 metals supported on a metal-alumina spinel. The RWGS        product gas exits the RWGS reactor vessel.    -   3. Hydrogen and carbon dioxide are mixed and fed into a Reverse        Water Gas Shift “RWGS” catalytic reactor at a ratio of H₂/CO₂        between 2.5 v/v to 4.5 v/v, or preferably 3.0 v/v to 4.0 v/v,        where the RWGS reactor vessel is adiabatic or nearly adiabatic.        The main reactor vessel is an insulated steel vessel, and it        contains a catalyst bed including a supported catalyst where the        catalyst consists of one or more Group 1 and Group 2 metals        supported on a metal-alumina spinel. The RWGS product gas exits        the RWGS reactor vessel.    -   4. Hydrogen and carbon dioxide are mixed and fed into the “RWGS”        catalytic reactor at a ratio of H₂/CO₂ between 2.5 v/v to 4.5        v/v or preferably 23.0 v/v to 4.0 v/v, where the RWGS reactor        vessel where heat is added to the vessel to maintain an        isothermal or nearly isothermal temperature profile in the        vessel; heating is performed without the use of direct        combustion of a carbon containing gas. The main reactor vessel        is an insulated steel vessel, and it contains a catalyst bed        including a supported catalyst where the catalyst consists of        one or more Group 1 and Group 2 metals supported on a        metal-alumina spinel. The RWGS product gas exits the RWGS        reactor vessel.    -   5. Hydrogen and carbon dioxide are mixed, heated to an inlet        temperature greater than 1,400° F., preferably greater than        1,500° F., or more preferably greater than 1,600° F. and fed        into a Reverse Water Gas Shift “RWGS” catalytic reactor at a        ratio of H₂/CO₂ between 2.5 v/v to 4.5 v/v or preferably 3.0 v/v        to 4.0 v/v, where the RWGS reactor vessel is adiabatic or nearly        adiabatic. The main reactor vessel is an insulated steel vessel,        and it contains a catalyst bed including a supported catalyst        one or more Group 1 and Group 2 metals supported on a        metal-alumina spinel. RWGS product gas exits the RWGS reactor        vessel.    -   6. Hydrogen and carbon dioxide are mixed together, heated to an        inlet temperature greater than 1,400° F., preferably greater        than 1,500° F., or more preferably greater than 1,600° F. and        fed into a Reverse Water Gas Shift “RWGS” catalytic reactor at a        ratio of H₂/CO₂ between 2.5 v/v to 4.5 v/v, or preferably 3.0        v/v to 4.0 v/v, where the RWGS reactor vessel where heat is        added to the vessel to maintain an isothermal or nearly        isothermal temperature profile in the vessel; heating is        performed without the use of direct combustion of a carbon        containing gas. The main reactor vessel is an insulated steel        vessel, and it contains a catalyst bed including a supported        catalyst where the catalyst consists of one or more Group 1 and        Group 2 metals supported on a metal-alumina spinel. The RWGS        product gas exits the RWGS reactor vessel.    -   7. Hydrogen and carbon dioxide are mixed, heated to an inlet        temperature greater than 1,400° F., preferably greater than        1,500° F., and more preferably greater than 1,600° F. by an        electrically heated radiant furnace and fed into a RWGS        catalytic reactor at a ratio of H₂/CO₂ between 2.5 v/v to 4.5        v/v or preferably 3.0 v/v to 4.0 v/v, where the RWGS reactor        vessel is adiabatic or nearly adiabatic. The main reactor vessel        is an insulated steel vessel, and it contains a catalyst bed        including a supported catalyst where the catalyst consists of        one or more Group 1 and Group 2 metals supported on a        metal-alumina spinel. The RWGS product gas exits the RWGS        reactor vessel.    -   8. Hydrogen and carbon dioxide are mixed together, heated to an        inlet temperature greater than 1400° F. or greater than 1500° F.        by an electrically heated radiant furnace and fed into a Reverse        Water Gas Shift “RWGS” catalytic reactor at a ratio of H₂/CO₂        between 2.5 v/v to 4.5 v/v, or preferably 3.0 v/v to 4.0 v/v,        where the RWGS reactor vessel where heat is added to the vessel        to maintain an isothermal or nearly isothermal temperature        profile in the vessel; heating is performed without the use of        direct combustion of a carbon containing gas. The main reactor        vessel is an insulated steel vessel, and it contains a catalyst        bed including a supported catalyst where the catalyst consists        of one or more Group 1 and Group 2 metals supported on a        metal-alumina spinel. The RWGS product gas exits the RWGS        reactor vessel.    -   9. Hydrogen and carbon dioxide are mixed, heated to an inlet        temperature greater than 1,400° F., preferably greater than        1,500° F., or preferably greater than 1,600° F. by an        electrically heated radiant furnace and fed into a Reverse Water        Gas Shift “RWGS” catalytic reactor at a ratio of H₂/CO₂ between        2.5 v/v to 4.5 v/v or preferably 3.0 v/v to 4.0 v/v. The        electric usage by the radiant furnace is less than 0.5 MWh        electricity/metric ton of CO₂ or less than 0.4 MWh        electricity/metric ton of CO₂ or less than 0.2 MWh        electricity/metric ton of CO₂ in the feed gas. The RWGS reactor        vessel is adiabatic or nearly adiabatic. The main reactor vessel        is an insulated steel vessel, and it contains a catalyst bed        including a supported catalyst where the catalyst consists of        one or more Group 1 and Group 2 metals supported on a        metal-alumina spinel. The RWGS product gas exits the RWGS        reactor vessel.    -   10. Hydrogen and carbon dioxide are mixed, heated to an inlet        temperature greater than 1,400° F., preferably greater than        1,500° F., and more preferably greater than 1,600° F. by an        electrically heated radiant furnace and fed into a RWGS        catalytic reactor at a ratio of H₂/CO₂ between 2.5 v/v to 4.5        v/v and preferably 3.0 v/v to 4.0 v/v. The electric usage by the        radiant furnace is less than 0.5 MWh electricity/metric ton of        CO₂ or less than 0.4 MWh electricity/metric ton of CO₂ or less        than 0.2 MWh electricity/metric ton of CO₂ in the feed gas. The        RWGS reactor vessel where heat is added to the vessel to        maintain an isothermal or nearly isothermal temperature profile        in the vessel; heating is performed without the use of direct        combustion of a carbon containing gas. The main reactor vessel        is an insulated steel vessel, and it contains a catalyst bed        including a supported catalyst where the catalyst consists of        one or more Group 1 and Group 2 metals supported on a        metal-alumina spinel. The RWGS product gas exits the RWGS        reactor vessel.    -   11. Hydrogen and carbon dioxide are mixed, heated to an inlet        temperature greater than 1,400° F., preferably greater than        1,500° F., or more preferably greater then 1,600° F. by an        electrically heated radiant furnace and fed into a RWGS        catalytic reactor at a ratio of H₂/CO₂ between 2.5 v/v to 4.5        v/v or preferably 3.0 v/v to 4.0 v/v. The electric usage by the        radiant furnace is less than 0.5 MWh electricity/metric ton of        CO₂ or less than 0.4 MWh electricity/metric ton of CO₂ or less        than 0.2 MWh electricity/metric ton of CO₂ in the feed gas. The        RWGS reactor vessel is adiabatic or nearly adiabatic. The main        reactor vessel is an insulated steel vessel that is tubular        (length longer than diameter). The reactor contains a catalyst        bed including the improved supported catalyst, and it contains a        catalyst bed including a supported catalyst where the catalyst        consists of one or more Group 1 and Group 2 metals supported on        a metal-alumina spinel. The RWGS product gas exits the RWGS        reactor vessel.    -   12. Hydrogen and carbon dioxide are mixed together, heated to an        inlet temperature greater than 1,400° F., preferably greater        than 1,500° F., and more preferably greater than 1,600° F. by an        electrically heated radiant furnace and fed into a RWGS        catalytic reactor at a ratio of H₂/CO₂ between 2.5 v/v to 4.5        v/v, and preferably 3.0 v/v to 4.5 v/v. The electric usage by        the radiant furnace is less than 0.5 MWh electricity/metric ton        of CO₂ or less than 0.4 MWh electricity/metric ton of CO₂ or        less than 0.2 MWh electricity/metric ton of CO₂ in the feed gas.        The RWGS reactor vessel where heat is added to the vessel to        maintain an isothermal or nearly isothermal temperature profile        in the vessel; heating is performed without the use of direct        combustion of a carbon containing gas. The main reactor vessel        is an insulated steel vessel that is tubular (length longer than        diameter). The reactor contains a catalyst bed including a        supported catalyst, where the catalyst consists of one or more        Group 1 and Group 2 metals supported on a metal-alumina spinel.        The RWGS product gas exits the RWGS reactor vessel.    -   13. Hydrogen and carbon dioxide are mixed, heated to an inlet        temperature greater than 1,400° F., r preferably greater than        1,500° F., and more preferably greater than 1,600° F. by an        electrically heated radiant furnace and fed into RWGS catalytic        reactor at a ratio of H₂/CO₂ between 2.5 v/v to 4.5 v/v, and        preferably 3.0 v/v to 4.0 v/v. The electric usage by the radiant        furnace is less than 0.5 MWh electricity/metric ton of CO₂ or        less than 0.4 MWh electricity/metric ton of CO₂ or less than 0.2        MWh electricity/metric ton of CO₂ in the feed gas. The RWGS        reactor vessel is adiabatic or nearly adiabatic. The main        reactor vessel is an insulated steel vessel that is tubular        (length longer than diameter). The reactor contains a catalyst        bed including a supported catalyst where the catalyst consists        of one or more Group 1 and Group 2 metals supported on a        metal-alumina spinel. The RWGS product gas exits the RWGS        reactor vessel.

EXAMPLES Example 1: Process Flowsheet Results with Adiabatic MainReactor Vessel

FIG. 1 shows the overall process flow for this example. Table 1 showsthe stream summary for this flowsheet example. Stream Number 1 (CO₂) andStream Number 2 (Hydrogen from electrolysis) are mixed and form StreamNumber 3 which heated via indirect heat exchange from approximately70-984° F. This is the Feed Gas stream, stream 35, is the Heated FeedGas Stream. Electric heater unit 4 heats the feed gas from 984° F. to1,600° F. The pre-heater is an electric radiant furnace that uses 30.7MW of electricity to accomplish the heating. For this example, the mainreactor vessel unit 6 is adiabatic. Stream Number 7 is the Product Gas.The temperature of the product gas has fallen from 1600° F. to 144° F.The CO₂ conversion is 70 mol %. The pressure drops across the RWGSreactor unit 6 is 10 psi.

In this example, the Product Gas is heated back to 1600° F. in a secondpreheater unit 9 to produce stream 13 and is then reacted in a secondreactor vessel unit 10 to produce stream 14. The CO₂ conversion in thesecond reactor is 7%.

TABLE 1 Stream Summaries for Example 1 from Process Flow in FIG. 1Stream No. 1 2 3 5 7 13 14 Temp ° F. 61.0 70.0 983.9 1600.0 1447.91600.0 1491.8 Pres (psig) 60 60 56 55 45 44 34 Total 5525 13798 1932219322 18698 18698 19036 (lbmol/h) Total (lb./h) 243177 27813 270990270990 270990 270990 270990 Component mole frac Hydrogen 0.00 1.00 0.710.71 0.48 0.48 0.49 Carbon 0.00 0.00 0.00 0.00 0.19 0.19 0.20 MonoxideMethane 0.00 0.00 0.00 0.00 0.02 0.02 0.01 CO₂ 1.00 0.00 0.29 0.29 0.090.09 0.08 H₂O 0.00 0.00 0.00 0.00 0.22 0.22 0.22

1. A process for the conversion of a feed gas comprising carbon dioxideand hydrogen to a product gas comprising carbon monoxide and waterwhere: a. the feed gas is heated to an inlet temperature greater than1,400° F. in a preheater outside the main reactor vessel to produce aheated feed gas; b. the preheater uses electricity to generate heat andproduce the heated feed gas; c. the heated feed gas is sent to a mainreactor vessel; d. the main reactor vessel is maintained at or nearisothermal conditions; e. the main reactor vessel contains catalyst thatconverts the heated feed gas to the product gas. 2-12. (canceled) 13.The process of claim 1 wherein the carbon dioxide used comes frombiological processes.
 14. The process of claim 1 wherein the carbondioxide used comes from industrial processes.
 15. The Process of claim 1wherein the carbon dioxide used comes from atmospheric processes. 16.The process of claim 1 wherein the feed gas is heated using anelectrically heated radiant furnace.
 17. The process of claim 1 whereinthe feed gas is heated by convective heat transfer.
 18. The process ofclaim 1 wherein the shape and particle size of the catalyst particlesused in the main reactor vessel is managed such that pressure dropacross the reactor is less than 50 pounds per square inch.
 19. Theprocess of claim 1 wherein the catalyst particle is a porous materialwith an internal surface area greater than 20 m²/g.
 20. The process ofclaim 19 wherein the catalyst comprises a metal from Group 1 and Group 2supported ion a metal-alumina spinel.
 21. The process of claim 1 whereinthe feed gas has a ratio of H2/CO2 between 2.5 v/v to 4.5 v/v.
 22. Theprocess of claim 1 wherein the feed gas is heated to a temperaturegreater than 1400° F.
 23. The process of claim 22 wherein the feed isheated to a temperature greater than 1500° F.
 24. A process for theconversion of a feed gas comprising carbon dioxide and hydrogen to aproduct gas comprising carbon monoxide and water where: a. the feed gasis heated to an inlet temperature greater than 1,400° F. in a preheateroutside the main reactor vessel to produce a heated feed gas; b. thepreheater uses electricity to generate heat and produce the heated feedgas; c. the heated feed gas is sent to a main reactor vessel; d. themain reactor vessel is an adiabatic or nearly adiabatic vessel whereheat loss is minimized; e. the main reactor vessel contains catalystthat converts the heated feed gas to the product gas; f. the product gasleaves the main reactor at an exit temperature where the exittemperature is lower than the inlet temperature.
 25. The process ofclaim 24 wherein the carbon dioxide used comes from biologicalprocesses.
 26. The process of claim 24 wherein the carbon dioxide usedcomes from industrial processes.
 27. The Process of claim 24 wherein thecarbon dioxide used comes from atmospheric processes.
 28. The process ofclaim 24 wherein the feed gas is heated using an electrically heatedradiant furnace.
 29. The process of claim 24 wherein the feed gas isheated by convective heat transfer.
 30. The process of claim 24 whereinthe shape and particle size of the catalyst particles used in the mainreactor vessel is managed such that pressure drop across the reactor isless than 50 pounds per square inch.
 31. The process of claim 24 whereinthe catalyst particle is a porous material with an internal surface areagreater than 20 m²/g.
 32. The process of claim 31 wherein the catalystcomprises a metal from Group 1 and Group 2 supported on a metal-aluminaspinel.
 33. The process of claim 24 wherein the feed gas has a ratio ofH2/CO2 between 2.5 v/v to 4.5 v/v.
 34. The process of claim 24 whereinthe feed gas is heated to a temperature greater than 1400° F.
 35. Theprocess of claim 34 wherein the feed is heated to a temperature greaterthan 1500° F.